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1
Kargin, Alexey Vladimirovich, Anna Andreevna Nosova, Ludmila Vyacheslavovna Sazonova, Vladimir Vasilievich Tretyachenko, Yulia Olegovna Larionova, and Elena Vladimirovna Kovalchuk. "Ultramafic Alkaline Rocks of Kepino Cluster, Arkhangelsk, Russia: Different Evolution of Kimberlite Melts in Sills and Pipes." Minerals 11, no. 5 (May 19, 2021): 540. http://dx.doi.org/10.3390/min11050540.
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To provide new insights into the evolution of kimberlitic magmas, we have undertaken a detailed petrographic and mineralogical investigation of highly evolved carbonate–phlogopite-bearing kimberlites of the Kepino cluster, Arkhangelsk kimberlite province, Russia. The Kepino kimberlites are represented by volcanoclastic breccias and massive macrocrystic units within pipes as well as coherent porphyritic kimberlites within sills. The volcanoclastic units from pipes are similar in petrography and mineral composition to archetypal (Group 1) kimberlite, whereas the sills represent evolved kimberlites that exhibit a wide variation in amounts of carbonate and phlogopite. The late-stage evolution of kimberlitic melts involves increasing oxygen fugacity and fluid-phase evolution (forming carbonate segregations by exsolution, etc.). These processes are accompanied by the transformation of primary Al- and Ti-bearing phlogopite toward tetraferriphlogopite and the transition of spinel compositions from magmatic chromite to magnesian ulvöspinel and titanomagnetite. Similar primary kimberlitic melts emplaced as sills and pipes may be transitional to carbonatite melts in the shallow crust. The kimberlitic pipes are characterised by low carbonate amounts that may reflect the fluid degassing process during an explosive emplacement of the pipes. The Kepino kimberlite age, determined as 397.3 ± 1.2 Ma, indicates two episodes of ultramafic alkaline magmatism in the Arkhangelsk province, the first producing non-economic evolved kimberlites of the Kepino cluster and the second producing economic-grade diamondiferous kimberlites.
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Kopylova, Maya G., and Patrick Hayman. "Petrology and textural classification of the Jericho kimberlite, northern Slave Province, Nunavut, Canada." Canadian Journal of Earth Sciences 45, no. 6 (June 2008): 701–23. http://dx.doi.org/10.1139/e08-011.
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The paper presents data on petrology, bulk rock and mineral compositions, and textural classification of the Middle Jurassic Jericho kimberlite (Slave craton, Canada). The kimberlite was emplaced as three steep-sided pipes in granite that was overlain by limestones and minor soft sediments. The pipes are infilled with hypabyssal and pyroclastic kimberlites and connected to a satellite pipe by a dyke. The Jericho kimberlite is classified as a Group Ia, lacking groundmass tetraferriphlogopite and containing monticellite pseudomorphs. The kimberlite formed during several consecutive emplacement events of compositionally different batches of kimberlite magma. Core-logging and thin-section observations identified at least two phases of hypabyssal kimberlites and three phases of pyroclastic kimberlites. Hypabyssal kimberlites intruded as a main dyke (HK1) and as late small-volume aphanitic and vesicular dykes. Massive pyroclastic kimberlite (MPK1) predominantly filled the northern and southern lobes of the pipe and formed from magma different from the HK1 magma. The MPK1 magma crystallized Ti-, Fe-, and Cr-rich phlogopite without rims of barian phlogopite, and clinopyroxene and spinel without atoll structures. MPK1 textures, superficially reminiscent of tuffisitic kimberlite, are caused by pervasive contamination by granite xenoliths. The next explosive events filled the central lobe with two varieties of pyroclastic kimberlite: (1) massive and (2) weakly bedded, normally graded pyroclastic kimberlite. The geology of the Jericho pipe differs from the geology of South African or the Prairie kimberlites, but may resemble Lac de Gras pipes, in which deeper erosion removed upper facies of resedimented kimberlites.
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Newton, David E., Amy G. Ryan, and Luke J. Hilchie. "Competence and lithostratigraphy of host rocks govern kimberlite pipe morphology." Canadian Journal of Earth Sciences 55, no. 2 (February 2018): 130–37. http://dx.doi.org/10.1139/cjes-2017-0019.
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We use analogue experimentation to test the hypothesis that host rock competence primarily determines the morphology of kimberlite pipes. Natural occurrences of kimberlite pipes are subdivided into three classes: class 1 pipes are steep-sided diatremes emplaced into crystalline rock; class 2 pipes have a wide, shallow crater emplaced into sedimentary rock overlain by unconsolidated sediments; class 3 pipes comprise a steep-sided diatreme with a shallow-angled crater emplaced into competent crystalline rock overlain by unconsolidated sediments. We use different configurations of three analogue materials with varying cohesions to model the contrasting geological settings observed in nature. Pulses of compressed air, representing the energy of the gas-rich head of a kimberlitic magma, are used to disrupt the experimental substrate. In our experiments, the competence and configuration of the analogue materials control the excavation processes as well as the final shape of the analogue pipes: eruption through competent analogue strata results in steep-sided analogue pipes; eruption through weak analogue strata results in wide, shallow analogue pipes; eruption through intermediate strength analogue strata results in analogue pipes with a shallow crater and a steep-sided diatreme. These experimental results correspond with the shapes of natural kimberlite pipes, and demonstrate that variations in the lithology of the host rock are sufficient to generate classic kimberlite pipe shapes. These findings are consistent with models that ascribe the pipe morphologies of natural kimberlites to the competence of the host rocks in which they are emplaced.
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Yakovlev, Evgeny Yu. "Features of radioactive element distribution within the Arkhangelsk diamondiferous province: possible directions for development of isotope–radiogeochemical methods for kimberlite prospecting in complex landscape–geology and climate conditions of the subarctic zone." Geochemistry: Exploration, Environment, Analysis 20, no. 3 (July 3, 2019): 269–79. http://dx.doi.org/10.1144/geochem2019-023.
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The effectiveness of traditional methods of searching for kimberlite pipes in the Arkhangelsk diamondiferous province (in the subarctic zone of Russia) has decreased greatly in recent years, and new methods of kimberlite exploration must therefore be developed. This study discusses new patterns of the distribution of natural radioactive isotopes within the Arkhangelsk diamondiferous province (Zolotitskoe kimberlite field), and the uranium isotopes 234U and 238U in particular. A variety of isotope radiogeochemical studies has shown that the kimberlite pipes are characterized by local radioisotope anomalies, on the surface and in exploration drill cores. These irregularities are clearly manifested in the formation of a non-equilibrium anomalous uranium isotope composition in the surrounding rocks and groundwater of the near-contact zone of the pipes. These uranium isotopes can be used to explore for kimberlites in other areas with similar complex landscape–geology and climate conditions of the subarctic zone.
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Azarova, N. S., A. V. Bovkun, V. K. Garanin, D. A. Varlamov, and H. L. Hong. "Oxide minerals of Kaavi kimberlites (Finland)." Proceedings of higher educational establishments. Geology and Exploration, no. 5 (November 28, 2019): 36–49. http://dx.doi.org/10.32454/0016-7762-2019-5-36-49.
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The mineralogical and petrogeochemical features of the Neoproterozoic kimberlite rocks of the Lahtojoki and Niilonsuo pipes of the Kaavi cluster (Kaavi-Kuopio, Finland) have been studied, differences in their petrogeochemical composition, quantitative and chemical composition of oxide minerals of deep (mantle) and kimberlite genesis have been revealed. The kimberlites of the pipes are moderately titanic, but the TiO2 content in the kimberlites of Niilonsuo is higher (2.11 wt.%) than in the kimberlites from the breccia of the Lahtojoki pipe (1.07 wt.%). The kimberlites of the Niilonsuo pipe also differ in higher concentrations of Fe2 O3 , Ca, P, K, Rb, V, Nb, Ba, Th, U, Ta and REE. In the Lahtojoki kimberlite breccias the main TiO2 concentrator mineral is magnesian ilmenite (13,3—15,2 wt.% MgO; 0,5—4,4 wt.% Cr2 O3 ), (macrocrysts up to 4 mm); the fine-grained matrix of rocks contains small grains of rutile, chromespinelides, Mn-ilmenite and sometimes titanomagnetite. Macrocrystals of magnesian ilmenite have been not found in the kimberlites of the Niilonsuo pipe, perovskite acts as the main mineral of titanium, and chromespinelids and titanomagnetite are less common. Long-term crystallization of relatively large (up to 200 μm) perovskite grains proceeded according to estimates using an Nb-Fe-perovskite oxybarometer under a wide range of oxygen fugacity (fо2 ) of the kimberlite melt (NNO from -3,8 to 5,1). Chromespinelids from the groundmass of kimberlite pipe rocks differ in composition, but have the same specific zonality — enrichment of Al and Mg in the edge zones of crystals, which is possibly due to the dissolution of phlogopite phenocrysts in the rising kimberlite melt. In addition to oxide minerals, djerfisherite is widely distributed in the groundmass of kimberlites of the Niilonsuo pipe, the composition of which for the rocks of the body has been described for the first time. The combination of features of oxide mineralization indicates unfavorable conditions for the preservation of diamonds during their transportation by kimberlite melt.
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Russell, J. Kelly, R. Stephen J. Sparks, and Janine L. Kavanagh. "Kimberlite Volcanology: Transport, Ascent, and Eruption." Elements 15, no. 6 (December 1, 2019): 405–10. http://dx.doi.org/10.2138/gselements.15.6.405.
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Kimberlite rocks and deposits are the eruption products of volatile-rich, silica-poor ultrabasic magmas that originate as small-degree mantle melts at depths in excess of 200 km. Many kimberlites are emplaced as subsurface cylindrical-to-conical pipes and associated sills and dykes. Surficial volcanic deposits of kimberlite are rare. Although kimberlite magmas have distinctive chemical and physical properties, their eruption styles, intensities and durations are similar to conventional volcanoes. Rates of magma ascent and transport through the cratonic lithosphere are informed by mantle cargo entrained by kimberlite, by the geometries of kimberlite dykes exposed in diamond mines, and by laboratory-based studies of dyke mechanics. Outstanding questions concern the mechanisms that trigger and control the rates of kimberlite magmatism.
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Yakovlev, Evgeny, and Andrey Puchkov. "Radon over Kimberlite Pipes: Estimation of the Emanation Properties of Rocks (Lomonosov Diamond Deposit, NW Russia)." Applied Sciences 11, no. 13 (June 29, 2021): 6065. http://dx.doi.org/10.3390/app11136065.
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In this paper, using the example of the Lomonosov diamond deposit, experimental studies of rocks were carried out to assess the main radiation and physical factors affecting the formation of the radon field over the kimberlite pipes of the Arkhangelsk diamondiferous province. For various types of rocks, represented by vent kimberlites, tuffaceous-sedimentary rocks of the crater and enclosing and overlying sediments, the following were studied: porosity, density, activity of radium-226, activity of radon in a free state, level of radon production, and emanation coefficient. The research results showed that the greatest amount of radon in a free state is produced by rocks of the near-pipe space, represented by the enclosing Vendian V2 deposits and characterized by high values of the emanation coefficient, radium activity, radon production level and porosity. This fact is associated with the structural and geological features of the near-pipe space, which was exposed to the impact of kimberlite magma on the host rocks. The lowest values of these parameters are characteristic of the kimberlites of the vent facies, which limits the formation of free radon in the body of the pipe. The results of the experimental studies create prospects for the development of emanation methods for searching for kimberlite pipes in the conditions of the Arkhangelsk diamondiferous province.
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Serebryakov, E. V., A. S. Gladkov, and D. A. Koshkarev. "Three‐dimensional structural‐material models of the formation of the Nyurbinskaya and Botuobinskaya kimberlite pipes (Yakutian Diamondiferous Province, Russia)." Geodynamics & Tectonophysics 10, no. 4 (December 11, 2019): 899–920. http://dx.doi.org/10.5800/gt-2019-10-4-0448.
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The Nyurbinskaya and Botuobinskaya kimberlitic pipes were in the focus of a comprehensive study aimed to investigate their structural and material positions as the main deposits in the Nakyn field (Yakutian Diamondife‐ rous Province, Russia). This paper present the study results and 3D structural‐material models showing the formation of these deposits. In application to geological studies, the 3D modeling technologies allow taking into account the ani‐ sotropy of material complexes comprising kimberlite pipes, as well as inconsistencies in the structural and morpho‐ logical properties of ore‐bearing structures. In order to discover the structural positions and features of the fault‐ block structures of the deposits, tectonophysical methods were used in combination with tacheometric surveys. Based on this more comprehensive and integrated approach, the existing fault patterns were clarified in detail; elements of the internal fault structure were mapped; fault azimuths and dip angles were estimated; and thickness values were obtained. Computer processed data were used to construct 3D models showing the fault‐block structures of the Nyurbinskaya and Botuobinskaya pipes. The mineralogical, petrographic and diamond‐bearing features of various kimberlite generations comprising these pipes were investigated in order to reconstruct the morphology and spatial positions of each of the selected complexes in the current cross‐section and in accordance with intrusion phases. The 3D frame models of geological bodies were constructed for all the magmatic phases, including porphyry kimberlite and eruptive and autolithic kimberlite breccia. The structural‐material models for the Nyurbinskaya and Botuobin‐ skaya pipes were based on a synthesis of their material and structural features discovered in the previous stages of the study. The models presented in this paper are used to discuss temporal relationships between faults in the kim‐ berlitic structure and material complexes comprising the pipes. The models show that the pipes occurred in the near‐ surface structures of shear tension, which developed in the areas where the NNE‐striking fault was conjugated with the ENE‐ and NE‐striking faults in the fault zone resulting from several stage of the tectono‐magmatic activity. In this case, the kimberlite melt material was transported in discrete portions from the source through deep‐seated faults, and the faults acted as channels characterized by an increased permeability. Disjunctive elements identified in this study facilitated magma movements and localization of kimberlite bodies.
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Smith, Richard S., A. Peter Annan, Jean Lemieux, and Rolf N. Pedersen. "Application of a modified GEOTEM® system to reconnaissance exploration for kimberlites in the Point Lake area, NWT, Canada." GEOPHYSICS 61, no. 1 (January 1996): 82–92. http://dx.doi.org/10.1190/1.1443959.
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Airborne geophysical surveying with electromagnetic (EM) and magnetic methods is an effective reconnaissance exploration tool for kimberlite pipes because the target can have an associated EM and magnetic anomaly. The EM response of kimberlite pipes is most often attributed to weathering alteration in a near‐surface layer, whereas the magnetic response is attributed to magnetite and ilmenite within the deeper unweathered kimberlite pipe. The discrete shape of kimberlite diatremes results in an easily identifiable anomaly pattern. Diamondiferous kimberlites have recently been found in the Northwest Territories (NWT) of Canada, an area glaciated in the Pleistocene and therefore devoid of a strongly weathered zone. By configuring the GEOTEM® airborne EM system to operate at high frequencies (270 Hz) and to take measurements while the transmitter is switched on, weakly conductive bodies may be detected because there is an adequate contrast with the surrounding highly resistive country rock. System modifications also allow the magnetic field to be sampled at an altitude of only 73 m instead of 120 m and ten times per second instead of once a second. This allows much better definition of weak, small magnetic anomalies. Data sets from two test areas (Point Lake and Willy Nilly, near Lac de Gras, NWT) demonstrate the effectiveness of the airborne system for reconnaissance surveying.
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Afanasiev, V. P., E. I. Nikolenko, N. V. Glushkova, and I. D. Zolnikov. "The new Massadou diamondiferous kimberlite field in Guinea." Геология рудных месторождений 61, no. 4 (August 13, 2019): 92–100. http://dx.doi.org/10.31857/s0016-777061492-100.
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A new kimberlite field, called Massadou, has been discovered in southeastern Guinea near Macenta city. The field consists of numerous ~1 m thick kimberlite dikes with low diamond contents; altogether 16 dikes have been found so far. Mineralization occurs along a 600 m wide zone distinct in satellite images, which is oriented in the same way as the K4 kimberlite reported by Huggerty. The Massadou kimberlite is covered by a thick laterite weathering profile. Main kimberlite indicator minerals found in the area are pyrope, chromite, and ilmenite. The latter occurs as zoned grains with a high-Fe core (hemoilmenite) surrounded by a parallel-columnar aggregate in the rim. The aggregate has a composition of ordinary kimberlitic Mg ilmenite and results from interaction of hemoilmenite with the kimberlite melt. The kimberlite age is estimated as 140—145 Ma by analogy with the surrounding fields. The dikes independent products of kimberlite magmatism in the Guinea-Liberia shield rather than being roots of pipes as interpreted by Skinner (2004). Therefore, the erosion cutout is moderate, and there are no reasons to expect the presence of large and rich diamond placers.
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Yudin, Denis, Nikolay Murzintsev, Alexey Travin, Taisiya Alifirova, Egor Zhimulev, and Sofya Novikova. "Studying the Stability of the K/Ar Isotopic System of Phlogopites in Conditions of High T, P: 40Ar/39Ar Dating, Laboratory Experiment, Numerical Simulation." Minerals 11, no. 2 (February 12, 2021): 192. http://dx.doi.org/10.3390/min11020192.
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Typically, 40Ar/39Ar dating of phlogopites from deep-seated xenoliths of kimberlite pipes produces estimates that suggest much older ages than those when these pipes were intruded. High-pressure (3 GPa) laboratory experiments enabled the authors to explore the behaviour of argon in the phlogopite structure under the conditions that correspond to the mantle, at the temperatures (from 700 to 1000 °С), far exceeding closure temperature of the K/Ar isotopic system. “Volume diffusion” remains foremost for describing the mobility of argon in phlogopite at high pressures. The mantle material age can be estimated through the dating of the phlogopites from deep-seated xenoliths of kimberlites, employing the 40Ar/39Ar method, subject to correction for a partial loss of radiogenic 40Ar when xenolith moves upwards to the Earth’s surface. The obtained data served as the basis for proposing the behaviour model of the K/Ar isotopic system of minerals in conditions of great depths (lower crust, mantle), and when transporting xenoliths in the kimberlite melt.
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Vasanthi, A., and K. Mallick. "Bouguer gravity anomalies and occurrence patterns of kimberlite pipes in Narayanpet-Maddur Regions, Andhra Pradesh, India." GEOPHYSICS 70, no. 1 (January 2005): J13—J24. http://dx.doi.org/10.1190/1.1852778.
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The Narayanpet Kimberlite field, that lies southwest of Hyderabad, the capital city of Andhra Pradesh, India, hosts a number of kimberlite pipes. These pipes appear to be randomly positioned. However, based on regional geologic structures revealed by Bouguer gravity anomalies, especially in a regional gravity map, their locations form a definite pattern. In the Narayanpet-Maddur region, regional Bouguer gravity contours exhibit some features of geologic interest: (1) the eastward convex regional contours show an increase in convexity from the Maddur and Kotakonda area on the east to Narayanpet on the west, (2) convexity is maximum in the vicinity of Narayanpet, where a large number of Kimberlite pipes occur nearly parallel to the regional contour, and (3) between Narayanpet and the Maddur-Kotakonda region, kimberlite pipes occur at intersections of three eastward, convex concentric zones with four lineaments, one trending northeast-southwest and the other three nearly east-west. These linear trends are believed to be radial, extensional, deep-fracture zones, through which kimberlite magma erupted about 1100 Ma. Modeling the residual gravity anomaly over one of the four profiles shows fairly good agreement between observed and computed fields. Based on analysis of Bouguer gravity anomalies and modeling of the residual gravity field, likely locations for kimberlite pipes are the contact zones between granite plutons and the country rocks that coincide with the northeast-southwest–trending radial faults that pass through Narayanpet and Kotakonda to the south and through Kazipur to the north.
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Kostrovitsky, S. I., D. A. Yakovlev, L. F. Suvorova, and E. I. Demonterova. "Carbonatite-Like Rock in a Dike of the Aikhal Kimberlite Pipe: Comparison with Carbonatites of the Nomokhtookh Site (Anabar Area)." Russian Geology and Geophysics 62, no. 6 (June 1, 2021): 605–18. http://dx.doi.org/10.2113/rgg20194086.
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Abstract ––A dike of rock similar in composition to carbonatites has been found in the Aikhal diamondiferous pipe of the Alakit–Markha field of the Yakutian kimberlite province (YaKP). The fine-grained rock of essentially carbonate composition (dolomite and calcite) rich in thin-platy phlogopite contains minerals typical of carbonatites: monazite, baddeleyite, and pyrochlore. In the high contents and distribution of incompatible elements the rock differs significantly from kimberlites and is transitional from kimberlites to carbonatites. The content of incompatible elements in this rock is 3–5 times lower than that in carbonatite breccias of the pipes in the Staraya Rechka kimberlite field of the YaKP (Nomokhtookh site). The compositions of accessory trace element minerals from the Aikhal dike rock and the Nomokhtookh carbonatite breccias are compared. An assumption is made that the high contents of incompatible elements in the carbonatite-like rock, which caused the crystallization of accessory minerals, are due to the differentiation of kimberlite melt/fluid. The high Sr isotope ratios indicate that the rock altered during hydrothermal and metasomatic processes. The obtained data on the composition of the carbonatite-like rock cannot serve as an argument for the genetic relationship between the Aikhal kimberlites and typical carbonatites. The genetic relationship between kimberlites and carbonatites in the northern fields of the YaKP remains an open issue.
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Giuliani, Andrea, and D. Graham Pearson. "Kimberlites: From Deep Earth to Diamond Mines." Elements 15, no. 6 (December 1, 2019): 377–80. http://dx.doi.org/10.2138/gselements.15.6.377.
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Kimberlites are rare, enigmatic, low-volume igneous rocks. They are highly enriched in magnesium, volatiles (CO2 and H2O) and incompatible trace elements and are thought to be the most deeply derived (>150 km) magmatic rocks on Earth. Kimberlites occur in ancient and thick continental lithosphere, forming intrusive sheets and composite pipes, commonly in clusters. Despite their rarity, kimberlites have attracted considerable attention because they entrain not only abundant mantle fragments but also diamonds, which can provide a uniquely rich picture of the deep Earth. This issue summarises current thinking on kimberlite petrology, geochemistry, and volcanology and outlines the outstanding questions on the genesis of kimberlites and associated diamond mines.
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Kang, Seogi, Dominique Fournier, and Douglas W. Oldenburg. "Inversion of airborne geophysics over the DO-27/DO-18 kimberlites — Part 3: Induced polarization." Interpretation 5, no. 3 (August 31, 2017): T327—T340. http://dx.doi.org/10.1190/int-2016-0141.1.
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The geologically distinct DO-27 and DO-18 kimberlites, often called the Tli Kwi Cho (TKC) kimberlites, have been used as a testbed for airborne geophysical methods applied to kimberlite exploration. This paper focuses on extracting chargeability information from time-domain electromagnetic (TEM) data. Three different TEM surveys, having similar coincident-loop geometry, have been carried out over TKC. Each records negative transients over the main kimberlite units and this is a signature of induced polarization (IP) effects. By applying a TEM-IP inversion workflow to a versatile time domain EM (VTEM) data set we decouple the EM and IP responses in the observations and then recover 3D pseudo-chargeability models at multiple times. A subsequent analysis is used to recover Cole-Cole parameters. Our models demonstrate that both DO-18 and DO-27 pipes are chargeable, but they have different Cole-Cole time constants: 110 and 1160 μs, respectively. At DO-27, we also distinguish between two adjacent kimberlite units based on their respective Cole-Cole time constants. Our chargeability models are combined with the density, magnetic susceptibility and conductivity models to build a 3D petrophysical model of TKC using only information obtained from airborne geophysics. Comparison of this final petrophysical model to a 3D geological model derived from the extensive drilling program demonstrates that we can characterize the three main kimberlite units at TKC: HK, VK, and PK in three dimensions by using airborne geophysics.
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ZINCHUK, NIKOLAI. "Typomorphic properties of kimberlite indicator minerals and their use in forecasting diamond deposits on the Siberian Platform." Domestic geology, no. 2 (May 27, 2021): 41–56. http://dx.doi.org/10.47765/0869-7175-2021-10012.
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The results of mantle nodule investigations in kimberlite diatremes of the main Siberian Platform diamondiferous regions were analyzed. Morphology and chemistry of garnets, chrome-diopsides, clinopyroxenes, olivines, picro-ilmenites, chromites, chrome-spinellids and diamonds were investigated in detail. Generally, the quantity of diamond association minerals is proportional to diamond potential of a certain kimberlite variety for each type of kimberlite rocks composing pipes.
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Gernon, Thomas M., R. Stephen J. Sparks, and Matthew Field. "Degassing structures in volcaniclastic kimberlite: Examples from southern African kimberlite pipes." Journal of Volcanology and Geothermal Research 174, no. 1-3 (June 2008): 186–94. http://dx.doi.org/10.1016/j.jvolgeores.2007.12.035.
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Zinchuk, N. N. "Geological and Petrographic Characteristics of Kimberlite Pipes." Вестник Пермского университета. Геология 4, no. 33 (December 26, 2016): 70–89. http://dx.doi.org/10.17072/psu.geol.33.70.
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Meyer, Tom. "Processing gravity gradients to detect kimberlite pipes." ASEG Extended Abstracts 2015, no. 1 (December 2015): 1–4. http://dx.doi.org/10.1071/aseg2015ab114.
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Oparin, Nikolay, and Oleg Oleynikov. "Picroilmenite from Kimberlite Pipes of Central Yakutia." IOP Conference Series: Earth and Environmental Science 609 (December 16, 2020): 012028. http://dx.doi.org/10.1088/1755-1315/609/1/012028.
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Ashchepkov, I. V., N. V. Alymova, A. M. Logvinova, N. V. Vladykin, S. S. Kuligin, S. I. Mityukhin, Y. B. Stegnitsky, et al. "Picroilmenites in Yakutian kimberlites: variations and genetic models." Solid Earth Discussions 5, no. 2 (August 20, 2013): 1259–334. http://dx.doi.org/10.5194/sed-5-1259-2013.
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Abstract. Major and trace element variations in picroilmenites from Late Devonian kimberlite pipes in Siberia reveal similarities within the region in general, but show individual features for ilmenites from different fields and pipes. Empirical ilmenite thermobarometry (Ashchepkov et al., 2010), as well as common methods of mantle thermobarometry and trace element geochemical modelling shows that long compositional trends for the ilmenites are a result of complex processes of polybaric fractionation of protokimberlite melts, accompanied by the interaction with mantle wall rocks and dissolution of previous wall rock and metasomatic associations. Evolution of picroilmenite's parental magmas was estimated for the three distinct phases of kimberlite activity from Yubileynaya and closely located Aprelskaya pipes showing heating and increase of Fe of mantle peridotites minerals from stage to stage and splitting of the magmatic system in the final stages. High pressure (5.5–7.0 GPa) Cr-bearing Mg-rich ilmenites (Group 1) reflect the conditions of high temperature metasomatic rocks at the base of the mantle lithosphere. Trace element patterns are enriched to 0.1–10/C1 and have flattened, spoon-like or S- or W-shaped REE patterns with Pb > 1. These result from melting and crystallization in melt – feeding channels in the base of the lithosphere, where high temperature dunite – harzburgites and pyroxenites were formed. Cr-poor ilmenite megacrysts (group2) trace the high temperature path of protokimberlites developed as result of fractional crystallization and wall rock assimilation during the creation of the feeder systems prior to the main kimberlite eruption. Inflections in ilmenite compositional trends probably reflect the mantle layering and pulsing melt intrusion during the melt migration within the channels. Group 2 ilmenites reveal inclined REE enriched patterns (10–100)/C1 with La/Ybn 10–25 similar to those derived from kimberlites, and HFSE peaks (typical megacrysts). A series of similar patterns results from polybaric AFC crystallization of protokimberlite melts which also precipitated sulfides (Pb < 1) and mixed with partial melts from garnet peridotites. Relatively low-Ti ilmenites with high Cr content (Group 3) probably crystallized in the metasomatic front under the rising protokimberlite source and represent the product of crystallization of segregated partial melts from metasomatic rocks. Cr- rich ilmenites are typical for veins and veinlets in peridotites crystallized from highly contaminated magma intruded into wall rocks in different levels within the mantle columns. The highest in TRE ilmenites 1000/C1 have REE patterns similar to those of perovskites. Low Cr contents suggest relatively closed system fractionation which occurred from the base of the lithosphere up to the garnet – spinel transition, according to monomineral thermobarometry for Mir and Dachnaya pipes. Restricted trends were detected for ilmenites from Udachnaya and most other pipes from the Daldyn -Alakit fields and other regions (Nakyn, Upper Muna and Prianabarie), where ilmenite trends extend from the base of the lithosphere mainly up to 4.0 GPa. Interaction of the megacryst-forming melts with the mantle lithosphere caused heating and HFSE metasomatism prior to kimberlite eruption.
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Menezes, Paulo T., and Mauricio D. García. "Kimberlite exploration at Serra da Canastra province, Brazil." GEOPHYSICS 72, no. 3 (May 2007): M1—M5. http://dx.doi.org/10.1190/1.2710352.
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Kimberlite and lamproite pipes are the only economically significant source rocks forming primary diamond deposits. Brazil, the world’s seventh largest diamond producer, has all of its production from alluvial deposits. The quest for a primary deposit has continued over several decades with very few positive results. To that end, airborne magnetic data from the Serra da Canastra diamondiferous province was used to identify kimberlite signatures. Serra da Canastra is located in the central portion of the Brazilian province in a low-magnetic-latitude region. The main tectonic feature of the area is a northwest-southeast major crustal fracture zone that extends for more than [Formula: see text] within the territory. The interpretation strategy was based on joint analysis of analytic signal and Euler deconvolution. A selected kimberlite target should typically have a roughly circular analytic signal anomaly coincident with a depth [Formula: see text] and structural [Formula: see text] constrained Euler solution. The proposed approach led to recognition of previously known pipes and generation of new targets. Ground geologic, geophysical, and geochemical follow-up surveys are necessary to test these selected targets.
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Smith, C. B., K. Sims, L. Chimuka, A. Duffin, A. D. Beard, and R. Townend. "Kimberlite metasomatism at Murowa and Sese pipes, Zimbabwe." Lithos 76, no. 1-4 (September 2004): 219–32. http://dx.doi.org/10.1016/j.lithos.2004.03.009.
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Khar'kiv, A. D. "STRUCTURE AND COMPOSITION OF SLIGHTLY ERODED KIMBERLITE PIPES." International Geology Review 32, no. 4 (April 1990): 404–14. http://dx.doi.org/10.1080/00206819009465787.
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Urosevic, Milovan, and Brian J. Evans. "Seismic methods for the detection of kimberlite pipes." Exploration Geophysics 29, no. 3-4 (September 1998): 632–35. http://dx.doi.org/10.1071/eg998632.
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Ashchepkov, I. V., N. V. Alymova, A. M. Logvinova, N. V. Vladykin, S. S. Kuligin, S. I. Mityukhin, H. Downes, et al. "Picroilmenites in Yakutian kimberlites: variations and genetic models." Solid Earth 5, no. 2 (September 2, 2014): 915–38. http://dx.doi.org/10.5194/se-5-915-2014.
Full textAbstract:
Abstract. Major and trace element variations in picroilmenites from Late Devonian kimberlite pipes in Siberia reveal similarities within the region in general, but show individual features for ilmenites from different fields and pipes. Empirical ilmenite thermobarometry (Ashchepkov et al., 2010), as well as common methods of mantle thermobarometry and trace element geochemical modeling, shows long compositional trends for the ilmenites. These are a result of complex processes of polybaric fractionation of protokimberlite melts, accompanied by the interaction with mantle wall rocks and dissolution of previous wall rock and metasomatic associations. Evolution of the parental magmas for the picroilmenites was determined for the three distinct phases of kimberlite activity from Yubileynaya and nearby Aprelskaya pipes, showing heating and an increase of Fe# (Fe# = Fe / (Fe + Mg) a.u.) of mantle peridotite minerals from stage to stage and splitting of the magmatic system in the final stages. High-pressure (5.5–7.0 GPa) Cr-bearing Mg-rich ilmenites (group 1) reflect the conditions of high-temperature metasomatic rocks at the base of the mantle lithosphere. Trace element patterns are enriched to 0.1–10/relative to primitive mantle (PM) and have flattened, spoon-like or S- or W-shaped rare earth element (REE) patterns with Pb > 1. These result from melting and crystallization in melt-feeding channels in the base of the lithosphere, where high-temperature dunites, harzburgites and pyroxenites were formed. Cr-poor ilmenite megacrysts (group 2) trace the high-temperature path of protokimberlites developed as result of fractional crystallization and wall rock assimilation during the creation of the feeder systems prior to the main kimberlite eruption. Inflections in ilmenite compositional trends probably reflect the mantle layering and pulsing melt intrusion during melt migration within the channels. Group 2 ilmenites have inclined REE enriched patterns (10–100)/PM with La / Ybn ~ 10–25, similar to those derived from kimberlites, with high-field-strength elements (HFSE) peaks (typical megacrysts). A series of similar patterns results from polybaric Assimilation + fractional crystallization (AFC) crystallization of protokimberlite melts which also precipitated sulfides (Pb < 1) and mixed with partial melts from garnet peridotites. Relatively low-Ti ilmenites with high-Cr content (group 3) probably crystallized in the metasomatic front under the rising protokimberlite source and represent the product of crystallization of segregated partial melts from metasomatic rocks. Cr-rich ilmenites are typical of veins and veinlets in peridotites crystallized from highly contaminated magma intruded into wall rocks in different levels within the mantle columns. Ilmenites which have the highest trace element contents (1000/PM) have REE patterns similar to those of perovskites. Low Cr contents suggest relatively closed system fractionation which occurred from the base of the lithosphere up to the garnet–spinel transition, according to monomineral thermobarometry for Mir and Dachnaya pipes. Restricted trends were detected for ilmenites from Udachnaya and most other pipes from the Daldyn–Alakit fields and other regions (Nakyn, Upper Muna and Prianabarie), where ilmenite trends extend from the base of the lithosphere mainly up to 4.0 GPa. Interaction of the megacryst forming melts with the mantle lithosphere caused heating and HFSE metasomatism prior to kimberlite eruption.
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Ishmukhametova, V. T. "FORECASTING OF KIMBERLITE DIAMOND DEPOSITS IN THE NORTH OF THE SIBERIAN PLATFORM ON THE BASIS OF INTERPRETATION OF SATELLITE IMAGES." Moscow University Bulletin. Series 4. Geology, no. 4 (August 28, 2016): 59–62. http://dx.doi.org/10.33623/0579-9406-2016-4-59-62.
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Essentially new method of allocation of diamondiferous kimberlite pipes against surrounding rocks is proposed. The method is based on interpretation of multispectral satellite images LANDSAT-7 ETM+ and allows to localize the most promising areas within perspective sites revealed by other methods. It was demonstrated that application of GIS-technologies for complex use of geological, geophysical, mineralogical data and results of interpretation of satellite images is efficient in forecasting kimberlite diamond deposits in both studied areas and poorly explored territories.
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Orr, Pauline, and Robert W. Luth. "Petrology and oxygen-isotope geochemistry of the Yamba Lake kimberlite rocks, N.W.T." Canadian Journal of Earth Sciences 37, no. 7 (July 1, 2000): 1053–71. http://dx.doi.org/10.1139/e00-021.
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The Torrie, Sputnik, and Eddie kimberlite rocks, located near Yamba Lake, central Slave province, N.W.T., are volcaniclastic, macrocrystic, heterolithic, olivine-rich tuff, and olivine-rich tuff breccia. Torrie and Sputnik kimberlite rocks contain pyroxene and garnet xenocrysts and megacrysts with major-element compositions consistent with derivation mostly from disaggregated garnet lherzolite, with subordinate contributions from eclogite, spinel lherzolite, garnet harzburgite, and websterite. The presence of primary groundmass phlogopite and compositionally evolved spinel, and the absence of mantle xenocrysts, xenoliths, and megacrystic ilmenite distinguish the Eddie kimberlite pipe from the other two kimberlite pipes. Large variations in δ18O of garnet and clinopyroxene in xenocrysts and xenoliths (+3.98 to +6.36), nonequilibrium intermineral isotopic fractionation, and major-element heterogeneity are interpreted as resulting from infiltration of fluids or melts produced by dehydration or melting of subducted oceanic crust into overlying peridotite. Although the timing is unconstrained for the xenocysts, the xenolith must have experienced this metasomatic interaction shortly before entrainment in the kimberlite. Variable δ18O values for magnesian ilmenite are also interpreted to result indirectly from such metasomatic activity in the mantle as well. The Torrie and Sputnik kimberlite rocks have low concentrations of diamond indicator minerals consistent with their low-diamond grades. These kimberlite rocks did not sample a significant amount of garnet harzburgite, the rock type commonly associated with high-diamond grades in other kimberlite rocks. Furthermore, metasomatism just prior to kimberlite eruption may have caused the resorption of any diamond present.
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Liu, Guimin, Peter Diorio, Peter Stone, Grant Lockhart, Asbjorn Christensen, Nick Fitton, and Mark Dransfield. "Detecting kimberlite pipes at Ekati with airborne gravity gradiometry." ASEG Extended Abstracts 2001, no. 1 (December 2001): 1–4. http://dx.doi.org/10.1071/aseg2001ab073.
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Bliss, James D. "Grade-tonnage and other models for diamond kimberlite pipes." Nonrenewable Resources 1, no. 3 (September 1992): 214–30. http://dx.doi.org/10.1007/bf01782275.
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PALKINA, O. Yu, and O. L. FALKOVICH. "Mineralogical Search Signs for Assessment of Prospects of Diamond Capacity of Ukraine (by Physiographical and Photoluminescent Data)." Mineralogical Journal 43, no. 1 (2021): 68–86. http://dx.doi.org/10.15407/mineraljournal.43.01.068.
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Some important questions concerning the application of methods of searches of diamond deposits on direct search signs - finds of diamonds are considered and indicator minerals of kimberlites (IMK). The probable reasons for the low efficiency of the dressing-mineralogical method in the search for diamond deposits in Ukraine are named. The article is based on materials of research of diamonds found in different age placers of Ukraine (~1300 crystals); diamonds from kimberlites of the Arkhangelsk province (~6000 crystals); diamonds from metamorphic rocks of the Kazakhstan deposit Kumdy-Kol (~200 crystals); Yakut province (~600 crystals from root springs and ~700 from placers). A physiographic description was made for all these crystals and the intensity and color of photoluminescence (PhL) were recorded. For some crystals, about 600 spectra were taken at a temperature of 77 K. For diamonds of the "Dniester" type and some highly defective diamonds from Ukrainian placers, data from Raman spectroscopy are given. The material on indicator minerals of kimberlites is partly the result of our research, partly attracted from literature sources. Finds of diamonds in terrigenous deposits of Ukraine, their territorial and age, possible sources of income are analyzed. The comparison of diamonds from terrigenous deposits of Ukraine with diamonds of indigenous deposits of different genetic type is performed. For comparison, we studied diamonds that were obtained (with their complete removal from the gross technological samples) from some kimberlite pipes of the Arkhangelsk province. We performed a physiographic description and established the particle size distribution and morphological distribution in these pipes. Based on these studies, convincing conclusions were drawn about the signs of the industrial diamond-bearing capacity of kimberlite bodies in this province. The study of a large number of diamonds extracted from Neogene and other placers of Ukraine allowed usto perform a comparative study not only on the morphology and color of photoluminescence but also on the frequency of photoluminescence centers (spectra were taken at 77K). These diamonds were compared with crystals from the industrial kimberlite bodies of the Arkhangelsk and Yakut provinces. It was established which physical properties of Ukrainian diamonds are close to the properties of kimberlite diamonds and how they differ, contrasting features of diamond sets of different genetic types were determined. It has been established that diamonds found in the deposits of the Bilokorovichi world have signs of kimberlite, and the nature of their surfaces, a set of PhL centers, indicates a long stay in sedimentary reservoirs of different ages. A study of diamonds and IMK, which were found on the territory of the Kirovohrad block of the Ukrainian Shield (USh), revealed that the known area of Gruzka has prospects and is worth further mineral and technological testing. The chemical composition of probable IMK from the kimberlite bodies of the Priazovsky block of the USh indicates their non-diamond-bearing or non-industrial diamond-bearing capacity, which is confirmed by a few (3 crystals) finds of natural diamonds. We found that the green microdiamonds extracted from these rocks turned out to be man-made debris. Numerous diamonds from Poltava-Sarmatian placers have specific morphology and physical properties. The source of diamonds from the Black Sea coast is the Poltava-Sarmatian placers, and the source of a few diamonds with kimberlite features has not been found on the coast of the Sea of Azov. Based on the analysis, it is concluded that the territory of Ukraine has clear prospects for the discovery of diamond deposits. Taking into account the current economic feasibility and the current degree of study of the diamond-bearing territory of Ukraine, the primary search for kimberlite sources of diamonds, in the opinion of the authors should be performed in the north-western (Ovruch-Bilokorovytsia) part, as well as within the Dnieper and Kirovograd blocks. In the course of search operations, it is necessary to abandon the analysis of IMC less than 1 mm in size and pay attention mainly to pyropes as the most informative IMC.A prerequisite for further exploration work for diamond deposits should be a large-scale mineralogical and technological test aimed at detecting diamonds with a size of at least 1.0 mm limiting the size of the studied fractions will allow not only to reduce costs, but also to determine the feasibility of the search.Only based on the results of these works it will be possible to concludethe prospects of the industrial diamond-bearing capacity of the allocated areas.
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da Costa, Alberto J. M. "Palmietfontein kimberlite pipe, South Africa—A case history." GEOPHYSICS 54, no. 6 (June 1989): 689–700. http://dx.doi.org/10.1190/1.1442697.
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The Palmietfontein kimberlite pipe is located 150 km northwest of Johannesburg, South Africa. It was emplaced at the contact between mafic rocks of the Bushveld complex and syenites of the Pilanesberg complex, and coincides with the intersection of two major faults. Palmietfontein is one of the larger known kimberlite pipes in South Africa; it has a surface area of 12 ha and is diamondiferous. The present geophysical study was designed to assist in planning an extensive program of trenching and drilling. Unweathered kimberlite has geophysical responses very similar to the country rock at Palmietfontein. Weathering and alteration of the upper 50 m of the pipe, however, have resulted in various physical changes, which has made the target amenable to investigation by various geophysical techniques. The surveys used in this study are gravity, electrical, seismic refraction, and airborne and ground magnetics and electromagnetics (EM). The boundary of the pipe was accurately defined, and the dip of the wallrock contact was determined by using various models and combinations of techniques. A small satellite body of kimberlite was also discovered during the course of this investigation. The most suitable techniques for kimberlite prospecting, particularly when the top portion of the kimberlite is weathered, are airborne EM and magnetics, combined with the Slingram ground-EM system. For more quantitative results, gravity and seismic surveys should be used.
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Zinchuk, N. N. "ABOUT LITHOMINERALOGICAL COMPOSITION OF ANCIENT SEDIMENTARY DIAMONDIFEROUS ROCKS." Proceedings of higher educational establishments. Geology and Exploration, no. 3 (June 25, 2018): 15–23. http://dx.doi.org/10.32454/0016-7762-2018-3-15-23.
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Litho-mineralogical and structural-formation generation features of Upper Devonian-Carboniferous crusts of weathering on terrigenous-carbonate rocks, kimberlites and deposits enriched by products of their redeposition, have been studied, that allowed restoring of the specific features of upper Paleozoic productive horizons generation of the main diamondiferous regions of the Siberian platform, and then, the areas, favorable for generation and preservation of kimberlite (including diamondiferous) material dispersion haloes, have been distinguished within them. Analysis of Upper Paleozoic deposits facies, as well as specific features of their location, has allowed to establish that denudation of the rocks of the region was insignificant since the moment of their crust formation and up to completion of upper Paleozoic sedimentation, and occurred only along the stream flows. The omnipresent availability of crusts of weathering on terrigenous-carbonate rocks of lower Paleozoic, preserved from washout by upper Paleozoic deposits, points on it. These formations are usually elongated in the form of narrow streams and represent fragments of most initial erosion of the crusts of weathering in post-Carboniferous time. That is why, at such minimal shear, practically all kimberlite minerals, occurring in Upper Paleozoic deposits, are redeposited from more ancient pre-Lapchanian formations. The necessity of differentiated approach to studying formation conditions of various facies of diamondiferous upper Paleozoic deposits of continental and coastal genesis has been substantiated, and firstly — studying of their specific features. The complex research is required, with application of structural-tectonic, lithological-facial and formation-cyclic analyses, which would allow allocating specific areas favorable for generation of ancient placers of diamonds or discovering kimberlite pipes.
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Hutchison, Mark T., Louise Josefine Nielsen, and Stefan Bernstein. "P–T history of kimberlite-hosted garnet lherzolites from South-West Greenland." Geological Survey of Denmark and Greenland (GEUS) Bulletin 13 (October 12, 2007): 45–48. http://dx.doi.org/10.34194/geusb.v13.4973.
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Exploration for diamonds in West Greenland has experienced a major boost within the last decade following the establishment of world-class diamond mines within the nearby Slave Province of the Canadian Arctic. Numerous companies have active programmes of diamond exploration and increasingly larger diamonds have been discovered, notably a 2.392 carat dodecahedral stone recovered by the Canadian exploration company Hudson Resources Inc. in January 2007. The Geological Survey of Denmark and Greenland (GEUS) is currently carrying out several studies aimed at understanding the petrogenesis of diamondiferous kimberlites in Greenland and the physical and chemical properties of their associated mantle source regions (e.g. Hutchison 2005; Nielsen & Jensen 2005). Constraint of the mantle geotherm, i.e. the variation of temperature with depth for a particular mantle volume, is an important initial step in assessing the likelihood of such a volume to grow diamonds and hence the diamond potential of associated deep-sourced magmatic rocks occurring at surface. Cool geotherms are often present within old cratonic blocks such as West Greenland (Garde et al. 2000) and provide a good environment for the formation of diamonds (Haggerty 1986). This study aims to constrain the mantle geotherm for the southern extent of the North Atlantic Craton in Greenland by applying three-phase geothermobarometry calculations using chemical compositions of clinopyroxene, orthopyroxene and garnet from four-phase kimberlite-hosted lherzolite xenoliths. Xenoliths have been sampled from kimberlites from two areas in South-West Greenland: Midternæs and Pyramide- fjeld (Fig. 1). Kimberlites in the Pyramidefjeld area principally occur as sheeted sills hosted in the Pyramidefjeld granite complex of Palaeoproterozoic Ketilidian age. In contrast, Midternæs kimberlites occur as outcrops within a single, extensive and undulating sill hosted within pre-Ketilidian granodioritic gneiss and Ketilidian supracrustal rocks. Pyramidefjeld kimberlites have been shown to be Mesozoic (Andrews & Emeleus 1971), and work is currently being carried out to further constrain the ages of these and the Midternæs kimberlites and also xenoliths using modern methods. No attempt is made herein to provide a correct petrological classification of the rocks hosting the xenoliths; however, the abundance of clinopyroxene reported by Andrews & Emeleus (1971) suggests that further work may more correctly conclude a classification as ‘orangeite’ after Mitchell (1995). Notwithstanding this, the term ‘kimberlite’ is employed throughout in order to be consistent with that adopted by previous authors. The Precambrian Pyramide fjeld granite complex and adjacent Archaean granod ioritic gneisses are host to several kimberlite sheets located at various levels between 400 and 900 m elevation (Fig. 1A; Andrews & Emeleus 1971, 1975). Kimberlites are mainly found as loose blocks in scree; however, these are almost always sourced locally from in situ bodies. Sheets can often be found deep within overhanging clefts, particularly in granitic walls. The kimberlite bodies are gently dipping, typically 20 degrees, and with a range of strikes. The maximum thickness of sills is approximately 2 m but thickness varies significantly over short distances. In many instances, the occurrence of kimberlite is seen to be controlled locally by structures in the country rocks. Field observations of the range of orientations of intrusive bodies do not appear to suggest a particular focal point which could be a likely location for an intrusive centre such as a pipe. This observation is in line with what is seen throughout West Greenland where kimberlite emplacement appears as dykes and sills (Larsen & Rex 1992) rather than the pipes and blows which are common in other world-wide settings. The occurrence of xenoliths amongst Pyramidefjeld kimberlites is highly variable with the most xenolith-rich localities being in the vicinity of Safirsø (Fig. 1A). The majority of xenoliths are dunites with occasional wehrlites and lherzolites (Emeleus & Andrews 1975). Of particular interest from the point of view of thermobarometry is the occurrence of garnet. This is rarely found, even in clinopyroxene-bearing samples, and the two samples chosen for thermobarometry (Fig. 1A) represent the majority of the garnet-bearing xenoliths identified within an estimated total population of 75 xenoliths collected. The Midternæs kimberlites are hosted in Archaean gneisses and Proterozoic supracrustal rocks (Fig. 1B; Andrews & Emeleus 1971, 1975). The style of kimberlite emplacement and occurrence of garnet-bearing xenoliths are closely similar to those of Pyramidefjeld. Contours of elevation between outcrops suggest that the kimberlites form parts of a largely contiguous single body dipping at approximately 30 degrees to the west-south-west. Individual outcrops as in Pyramidefjeld indicate that the body varies in thickness and undulates in response to local structure. The south-western portion of the body which outcrops near the glacier Sioralik Bræ, is considerably thicker than elsewhere (Fig. 2) and in some places is seen to have a true thickness in excess of 4 m. Xenoliths are less abundant on average than in Pyramidefjeld kimberlites, but a similar variety and proportion of rock types and infrequent occurrence of garnet is observed. The kimberlites from both areas were intruded along zones of platy jointing which likely were caused by degassing of the magma and formed just prior to the kimberlite intrusion. In contrast to some kimberlites in other cratons, very few xenoliths of local, lower crustal rock types have been recognised in the kimberlites from Pyramidefjeld and Mid ternæs. The intrusions are therefore believed to have been of a non-explosive nature, perhaps because of host-rock rheol - ogy or due to emplacement at relatively deep crustal levels. Here we report on calculations of equilibrium pressure and temperature using compositions of three-phase assemblages of garnet, orthopyroxene and clinopyroxene from Midternæs and Pyramidefjeld mantle xenoliths.
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Agasheva, Elena. "Magmatic Material in Sandstone Shows Prospects for New Diamond Deposits within the Northern East European Platform." Minerals 11, no. 4 (March 25, 2021): 339. http://dx.doi.org/10.3390/min11040339.
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A detailed study of sandstones recovered from the upper part of the recently discovered KL-01 magmatic pipe in the southern part of the Arkhangelsk diamondiferous province (ADP), containing magmatic material and rare kimberlite indicator minerals, is presented in this paper. Results are compared to the composition of crater samples of the highly diamondiferous Vladimir Grib kimberlite pipe and several poorly to non-diamondiferous ADP pipes. To identify the type of magmatic material admixture, a model of binary mixing between country Vendian sandstones and typical ADP magmatic rocks based on correlations of La/Yb and Zr/Nb ratios and Ni contents is proposed. The modeling results show that the type of magmatic component in the KL-01 samples can be identified as kimberlite, with a maximum admixture of 20 vol.%. Kimberlite indicator mineral geochemistry did not exclude the interpretation that the composition, structure, thermal state and metasomatic enrichment of the lithospheric mantle sampled by the KL-01 pipe were suitable for the formation and preservation of diamonds. The lower boundary of the sampled lithospheric mantle could be in the depth range of 175–190 km, with a diamond window width of 55–70 km. Thus, the sandstones could represent the upper level of the crater of a new kimberlite pipe.
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Dymshits, Anna M., Igor S. Sharygin, Vladimir G. Malkovets, Igor V. Yakovlev, Anastasia A. Gibsher, Taisia A. Alifirova, Sofya S. Vorobei, Sergey V. Potapov, and Viktor K. Garanin. "Thermal State, Thickness, and Composition of the Lithospheric Mantle beneath the Upper Muna Kimberlite Field (Siberian Craton) Constrained by Clinopyroxene Xenocrysts and Comparison with Daldyn and Mirny Fields." Minerals 10, no. 6 (June 18, 2020): 549. http://dx.doi.org/10.3390/min10060549.
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To gain better insight into the thermal state and composition of the lithospheric mantle beneath the Upper Muna kimberlite field (Siberian craton), a suite of 323 clinopyroxene xenocrysts and 10 mantle xenoliths from the Komsomolskaya-Magnitnaya (KM) pipe have been studied. We selected 188 clinopyroxene grains suitable for precise pressure (P)-temperature (T) estimation using single-clinopyroxene thermobarometry. The majority of P-T points lie along a narrow, elongated field in P-T space with a cluster of high-T and high-P points above 1300 °C, which deviates from the main P-T trend. The latter points may record a thermal event associated with kimberlite magmatism (a “stepped” or “kinked” geotherm). In order to eliminate these factors, the steady-state mantle paleogeotherm for the KM pipe at the time of initiation of kimberlite magmatism (Late Devonian–Early Carboniferous) was constrained by numerical fitting of P-T points below T = 1200 °C. The obtained mantle paleogeotherm is similar to the one from the nearby Novinka pipe, corresponding to a ~34–35 mW/m2 surface heat flux, 225–230 km lithospheric thickness, and 110–120 thick “diamond window” for the Upper Muna field. Coarse peridotite xenoliths are consistent in their P-T estimates with the steady-state mantle paleogeotherm derived from clinopyroxene xenocrysts, whereas porphyroclastic ones plot within the cluster of high-T and high-P clinopyroxene xenocrysts. Discrimination using Cr2O3 demonstrates that peridotitic clinopyroxene xenocrysts are prevalent (89%) among all studied 323 xenocrysts, suggesting that the Upper Muna mantle is predominantly composed of peridotites. Clinopyroxene-poor or -free peridotitic rocks such as harzburgites and dunites may be evident at depths of 140–180 km in the Upper Muna mantle. Judging solely from the thermal considerations and the thickness of the lithosphere, the KM and Novinka pipes should have excellent diamond potential. However, all pipes in the Upper Muna field have low diamond grades (<0.9, in carats/ton), although the lithosphere thickness is almost similar to the values obtained for the high-grade Udachnaya and Mir pipes from the Daldyn and Mirny fields, respectively. Therefore, other factors have affected the diamond grade of the Upper Muna kimberlite field.
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Kampata, M. D., J. Moreau, J. Hertogen, D. Demaiffe, E. Condliffe, and N. F. Mvuemba. "Megacrysts and ultramafic xenoliths from Kundelungu kimberlites (Shaba, Zaire)." Mineralogical Magazine 59, no. 397 (December 1995): 661–76. http://dx.doi.org/10.1180/minmag.1995.059.397.09.
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AbstractSome twenty kimberlite pipes outcrop along the eastern and western borders of the Kundelungu plateau, Shaba Province, Zaire. They are arranged roughly along two north-south trending alignments. The pipes probably intruded the Bangweulu Block, which stabilized around 1800 Ma. The exceptionally fresh kimberlites contain mantle-derived nodules (peridotites and eclogites), as well as megacrysts which may reach up to several cm in diameter. The most important megacrysts are garnets, ilmenites, clinopyroxenes, orthopyroxenes and olivines. Micas and diamonds are rarely observed. The clinopyroxenes can be subdivided in two groups: (1) a Ca-rich, low-T type, similar to the Cr-rich diopsides found in ‘depleted’ (granular) peridotites; and (2) subcalcic clinopyroxene comparable to the megacrysts and to the clinopyroxenes of ‘fertile’ (sheared) peridotites. The orthopyroxenes are less frequent and are Ca-poor enstatites (0.07–0.42 wt.% CaO) and Ti-bronzites (CaO <1.3 wt.%). All the analysed garnets are Ca-rich (>4.5 wt.% CaO) and all fall in the lherzolite field defined by Sobolev et al., 1973. The low-Ca garnets which appear in many diamond-bearing kimberlites have never been observed in Zaire, neither in the diamond-poor Kundelungu pipes nor in the diamond-rich Mbuji-Mayi pipes. The ilmenites define a trend close to the ‘magmatic Mg-enrichment trend';. The olivine macrocrysts have Fo contents comparable to those of peridotites (Fo90–93). The ultramafic nodules comprise lherzolites, harzburgites, pyroxenites, wehrlites and dunites. The granular textures and P-T equilibrium conditions (770–1380°C and 28–61 kbar) deduced from their mineral compositions, show clearly that they were derived from a mantle zone on the continental geotherm (90–190 km depth). The eclogite nodules, which are less frequent, contain only two mineral phases (pyrope-almandine-grossular and omphacite), and the texture and the mineral compositions are similar to those of Roberts Victor eclogites. Our findings support the conclusion of Nixon and Condliffe (1989) that low-T peridotites, eclogites and pyroxenites derived from ‘depleted’ lithosphere, while Cr-poor garnet, subcalcic diopside and bronzite megacrysts cristallized from fertile asthenosphere.
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Barnett, Wayne. "Subsidence breccias in kimberlite pipes—an application of fractal analysis." Lithos 76, no. 1-4 (September 2004): 299–316. http://dx.doi.org/10.1016/j.lithos.2004.03.019.
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Fournier, Dominique, Seogi Kang, Michael S. McMillan, and Douglas W. Oldenburg. "Inversion of airborne geophysics over the DO-27/DO-18 kimberlites — Part 2: Electromagnetics." Interpretation 5, no. 3 (August 31, 2017): T313—T325. http://dx.doi.org/10.1190/int-2016-0140.1.
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We focus on the task of finding a 3D conductivity structure for the DO-18 and DO-27 kimberlites, historically known as the Tli Kwi Cho (TKC) kimberlite complex in the Northwest Territories, Canada. Two airborne electromagnetic (EM) surveys are analyzed: a frequency-domain DIGHEM and a time-domain VTEM survey. Airborne time-domain data at TKC are particularly challenging because of the negative values that exist even at the earliest time channels. Heretofore, such data have not been inverted in three dimensions. In our analysis, we start by inverting frequency-domain data and positive VTEM data with a laterally constrained 1D inversion. This is important for assessing the noise levels associated with the data and for estimating the general conductivity structure. The analysis is then extended to a 3D inversion with our most recent optimized and parallelized inversion codes. We first address the issue about whether the conductivity anomaly is due to a shallow flat-lying conductor (associated with the lake bottom) or a vertical conductive pipe; we conclude that it is the latter. Both data sets are then cooperatively inverted to obtain a consistent 3D conductivity model for TKC that can be used for geologic interpretation. The conductivity model is then jointly interpreted with the density and magnetic susceptibility models from a previous paper. The addition of conductivity enriches the interpretation made with the potential fields in characterizing several distinct petrophysical kimberlite units. The final conductivity model also helps better define the lateral extent and upper boundary of the kimberlite pipes. This conductivity model is a crucial component of the follow-up paper in which our colleagues invert the airborne EM data to recover the time-dependent chargeability that further advances our geologic interpretation.
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Howarth, Geoffrey H., and E. Michael W. Skinner. "Sub-volcanic development of kimberlite pipes: Evidence from the Lace and Voorspoed (Group II) kimberlites, South Africa." Journal of Volcanology and Geothermal Research 268 (December 2013): 1–16. http://dx.doi.org/10.1016/j.jvolgeores.2013.10.002.
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Devriese, Sarah G. R., Kristofer Davis, and Douglas W. Oldenburg. "Inversion of airborne geophysics over the DO-27/DO-18 kimberlites — Part 1: Potential fields." Interpretation 5, no. 3 (August 31, 2017): T299—T311. http://dx.doi.org/10.1190/int-2016-0142.1.
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The Tli Kwi Cho (TKC) kimberlite complex contains two pipes, called DO-27 and DO-18, which were discovered during the Canadian diamond exploration rush in the 1990s. The complex has been used as a testbed for ground and airborne geophysics, and an abundance of data currently exist over the area. We have evaluated the historical and geologic background of the complex, the physical properties of interest for kimberlite exploration, and the geophysical surveys. We have carried out 3D inversion and joint interpretation of the potential field data. The magnetic data indicate high susceptibility at DO-18, and the magnetic inversion maps the horizontal extent of the pipe. DO-27 is more complicated. The northern part is highly magnetic and is contaminated with remanent magnetization; other parts of DO-27 have a low susceptibility. Low densities, obtained from the gravity and gravity gradiometry data, map the horizontal extents of DO-27 and DO-18. We combine the 3D density contrast and susceptibility models into a single geologic model that identifies three distinct kimberlite rock units that agree with drilling data. In further research, our density and magnetic susceptibility models are combined with information from electromagnetic data to provide a multigeophysical interpretation of the TKC kimberlite complex.
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Yang, Zhijun, Rong Liang, Xiangqing Zeng, and Mingsheng Peng. "A Microscopy and FTIR and PL Spectra Study of Polycrystalline Diamonds from Mengyin Kimberlite Pipes." ISRN Spectroscopy 2012 (April 22, 2012): 1–10. http://dx.doi.org/10.5402/2012/871824.
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The results of a microscopy and FTIR and PL spectra study of the natural polycrystalline diamonds from the Mengyin kimberlite pipes show that they can be classified as the euhedral faceted polycrystalline diamonds (EFPCDs) and anhedral rounded polycrystalline diamonds (ARPCDs). Different diamond grains or their points were formed in different conditions or processes. They were not formed in diamond nucleation stage, but in the diamond growth period. They probably originated from the relatively deeper mantle and were formed in the environment like the peridotitic (P) type diamond single crystals. The EFPCDs did not undergo a remarkable dissolution process during their formation and were possibly fast formed shortly before the kimberlite eruption. The ARPCDs not only were formed at a higher temperature than the EFPCDs but also underwent a notable dissolution process and had been stored relatively longer in the mantle. Fluids or melts probably participated in the formation of the ARPCDs or modified them during the period of their storage in the mantle.
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Yegorov, K. N. "CONTACT RELATIONSHIPS BETWEEN KIMBERLITE INJECTION PHASES IN PIPES WITH COMPLEX STRUCTURES." International Geology Review 27, no. 10 (October 1985): 1179–91. http://dx.doi.org/10.1080/00206818509466492.
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Urosevic, M., and B. J. Evans. "Surface and borehole seismic methods to delineate kimberlite pipes in Australia." Leading Edge 19, no. 7 (July 2000): 756–58. http://dx.doi.org/10.1190/1.1438712.
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Zinchenko, V. N. "Morphology of diamonds from kimberlite pipes of the Catoca field, Angola." Geology of Ore Deposits 50, no. 8 (December 2008): 806–14. http://dx.doi.org/10.1134/s1075701508080199.
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Ashchepkov, I. V., N. P. Pokhilenko, N. V. Vladykin, A. Y. Rotman, V. P. Afanasiev, A. M. Logvinova, S. I. Kostrovitsky, et al. "Reconstruction of mantle sections beneath Yakutian kimberlite pipes using monomineral thermobarometry." Geological Society, London, Special Publications 293, no. 1 (2008): 335–52. http://dx.doi.org/10.1144/sp293.15.
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Zen’kov, I. V., E. V. Kiryushina, A. S. Morin, V. N. Vokin, Zh V. Mironova, P. M. Kondrashov, A. B. Fedorov, and T. A. Veretenova. "Justification for the Reclamation of Rock Dumps and Reclaimed Ore Deposits in the Yakutia Diamond Deposits." Ecology and Industry of Russia 24, no. 1 (January 10, 2020): 51–55. http://dx.doi.org/10.18412/1816-0395-2020-1-51-55.
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The results of remote monitoring of the ecological state of waste dumps and storages of processed diamond-bearing rock are presented. Low rates of restoration of vegetation cover at these objects of the mining landscape, formed during the development of kimberlite pipes, were revealed. To accelerate the restoration of vegetation on the territory of disturbed lands, a set of special works on technical and biological reclamation is proposed.
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Nowicki, Tom, Barbara Crawford, Darren Dyck, Jon Carlson, Ross McElroy, Peter Oshust, and Herb Helmstaedt. "The geology of kimberlite pipes of the Ekati property, Northwest Territories, Canada." Lithos 76, no. 1-4 (September 2004): 1–27. http://dx.doi.org/10.1016/j.lithos.2004.03.020.
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Garanin, V. K., G. P. Kudryavtseva, A. A. Marakushev, A. F. Cherenkova, and V. G. Cherenkov. "A NEW VARIETY OF DEEP-SEATED HIGH-ALUMINA ROCK IN KIMBERLITE PIPES." International Geology Review 29, no. 11 (November 1987): 1366–76. http://dx.doi.org/10.1080/00206818709466231.
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Sarma, B. S. P., B. K. Verma, and S. V. Satyanarayana. "Magnetic mapping of Majhgawan diamond pipe of central India." GEOPHYSICS 64, no. 6 (November 1999): 1735–39. http://dx.doi.org/10.1190/1.1444678.
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Magnetic response over kimberlite/lamproite pipes can be used to map their horizontal and vertical cross‐sections. A published ground magnetic vertical intensity contour map is used to map the Majhgawan kimberlite pipe near Panna in central India. Using Barnett’s (1976) method, we obtained a reasonable match between the computed and observed fields with three separate bodies. The model suggests a possible later intrusion into the main pipe. Geological studies (using drill‐hole data) imply a nearly concentric vertical lithological zoning within the pipe and thus support the hypothesis of multiple intrusions, indicated by magnetic data. The multiple intrusion hypothesis is of interest to exploration because specific intrusions within one composite pipe may differ markedly in the incidence of diamonds. The higher incidence of diamonds reported in the central part of the Majhgawan pipe, as compared to the outer part, also supports the possibility of a later intrusion into the main pipe.